1. Field of Invention
The invention relates to an embroidery frame that comprises an outer frame to be attached to a driving unit of a frame drive mechanism of an embroidery sewing machine, and an inner frame that cooperates with the outer frame to hold a work cloth therebetween.
2. Description of Related Art
There are currently household embroidery sewing machines that incorporate embroidery devices and are capable of performing embroidery sewing operations, and household embroidery sewing machines to which embroidery devices may be optionally attached to enable embroidery sewing operations. By setting a work cloth in an embroidery frame and attaching the frame to a drive unit of the embroidery device, the above type of sewing machine is able to form desired embroidery patterns on the work cloth.
For use with the above-described embroidery sewing machines, various embroidery frames having different sizes are prepared depending upon the area of a desired embroidery region in which an embroidery pattern can be formed. As for the shape of the embroidery frame, those having a generally rectangular shape or generally circular shape have been widely used in practical applications. A typical embroidery frame consists of an outer frame to be attached to the drive unit of the embroidery device, and an inner frame that cooperates with the outer frame to sandwich a work cloth therebetween. Each of the inner and outer frames has predetermined front and rear sides or faces.
More specifically, the outer frame is equipped with a coupling member to be connected to the driving unit of the embroidery device, and therefore the front and rear sides of the outer frame are predetermined depending upon the mounting position or orientation of the coupling member relative to the outer frame, and mounting conditions that allow the inner frame to be easily fitted in the outer frame. On the other hand, the inner frame is formed with ribs so that the work cloth can be securely held between the inner and outer frames, to stretch over an opening defined by the frames without forming creases on the cloth set in the frames, thus preventing the work cloth from being loosened during embroidery sewing. Thus, the front and rear sides of the inner frame are also predetermined depending upon the location of the ribs.
Embroidery frames are often supplied as accessories with sewing machines capable of embroidery sewing and currently available in the market. Although the user's guide or manual provides brief instructions on how to use the embroidery frame, the user is apt to be confused at a glance into thinking that the embroidery frame has no front and rear sides. In fact, it is difficult for the user to tell or determine the front and rear sides of the embroidery frame only by looking at it for a short time. Accordingly, if the user is a beginner, and not accustomed to embroidery sewing operations, he/she is liable to make a basic mistake, by placing the outer frame on a table such that its rear side faces upward, laying a work cloth over the outer frame, and finally fitting the inner frame into the outer frame such that the rear side of the inner frame faces upwards. Since the embroidery frame cannot be attached to the driving unit of the embroidery device unless it is correctly oriented, the user may turn the embroidery frame upside down, and attach the frame to the embroidery device such that the front side of the outer frame faces upwards.
In the above case, the work cloth is set from the rear side of the embroidery frame while the rear sides of the outer frame and inner frame face are facing upwards, namely, the embroidery frame is oriented upside down, and then attached to the drive unit of the embroidery device in the normal state in which the front side of the outer frame faces upwards, namely, the embroidery frame is placed upside down. As a result, the work cloth is stretched over the upper face of the embroidery frame, and a sewing operation is performed on the work cloth that is being held at a position higher than that of the needle plate. This may cause such problems that a sewing needle that is driven in the vertical direction is undesirably caught by the work cloth, with the results that the cloth is torn apart, the needle is broken, or embroidery stitches are cut off by the sewing needle.
FIG. 11 shows a known example of embroidery frame (supplied with a sewing machine whose model number is HZL-008NIAT-5800, available from Tokyo Juki Industrial Co., Ltd.). The embroidery frame 100 consists of an outer frame 200 and an inner frame 300. The outer frame 200 is provided at one location thereof with a split portion 204, which can be fastened by a fastening mechanism 202. It is to be noted that no recessed portion other than the split portion 204 is provided on the circumference of the frame. On the other hand, the inner frame 300 includes a positioning protrusion 302 formed at one location on the side face of the frame, and a tab 304 formed on the upper face of the frame such that the tab 304 extends outwardly of the frame while slightly protruding upwards. When the inner frame 300 is correctly oriented and fitted in the outer frame 200, the protrusion 302 comes to be located in a clearance 206 of the split portion 204 of the outer frame 200. This arrangement makes it easy for the user to determine the front and rear sides of the inner frame 300, and prevents the inner frame 300 from being reversed and fitted in the outer frame 200 in the reversed state.
In the conventional embroidery frame 100 as described above, however, the split portion 204 of the outer frame 200 must provide a sufficiently large size of clearance 206. Therefore the tension of the cloth may be reduced in the vicinity of the split portion 204. Namely, a part of the cloth that faces the clearance 206 of the split portion 204 of the outer frame 200 is not sandwiched between the outer frame 200 and the inner frame 300, and only the inner frame 200 serves to support this part of the cloth to stretch it over the opening of the frame. In this part of the cloth having reduced tension creases are likely to appear, which may cause a problem during embroidery sewing.